1. Field of the Invention
The present invention relates to an image scanner used in a reader, a copying machine or the like.
2. Description of the Prior Art
In a prior art copying machine, an original sheet is illuminated by a light source such as a halogen lamp or a fluorescent lamp, light reflected thereby is condensed by a lens and focused on a photosensitive drum in the machine through a mirror. A latent image is formed on the photosensitive drum. Then, developer is applied to the photosensitive drum so that the developer is deposited in accordance with the latent image. Thus, the latent image is visualized. The image is then transferred to a plane paper so that the original document image is copied.
In such a copying machine, the light reflected by the original sheet must be directed to the photosensitive drum by the optical system such as a reflection mirror and a lens, or in a special case, an optical fiberscope.
Accordingly, in such a copying machine, magnification/reduction function, moving function, etc., of the original document image are attained by mechanical means.
For example, a desired magnification factor in the magnification/reduction operation is achieved by moving the lens to change a focal distance of the lens and changing a scan speed of the original sheet or a speed of the movement of the photosensitive drum.
When it is desired to transfer a portion of the original sheet image to a selected position on a copy paper, the image formation position on the copy paper is not adjustable because it is fixed by mechanical factors. Thus, a user first determines the portion of the original sheet to be copied and must position that portion on an area on an original sheet mount which corresponds to the desired copy area of the copy paper. Such positioning is incorrect and inaccurate, and in certain instances, a test copy must be made to check the positioning.